1. Field of the Invention
The present invention relates to a fail safe method and in a motor-driven power steering apparatus in which a steering apparatus of a car is subsidiarily energized by rotary force of an electric motor.
2. Background of The Invention
In the conventional power steering apparatus, force for turning a handle (steering torque), which is applied by a driver, has been detected by a torque sensor such that the steering torque is converted into a torsional angle displacement of a torsion bar or the like and the torsional angle of the torsion bar is converted into an electric signal by a potentiometer in the torque sensor.
In such an apparatus as described above, however, the signal of the torque sensor is received as an input to control a driving current of a motor as well as an electromagnetic clutch for subsidiarily energizing the steering apparatus through a control unit, and therefore there has been such a problem that the steering apparatus is turned right or left of itself against will of a driver to cause a danger in case of a failure in the torque sensor or the control unit so as to make it impossible to perform the control.